Visual primitives have long been proposed, under the name of geons or generalized cylinders, as components for object models in the brain and in the computer. Geons constitute a structural level intermediate between features and whole objects, and can form a basis for powerful generalization between different view points. We here present a system for the extraction of geon models from images of...

The nature of the obscuring material in active galactic nuclei is still uncertain. Although some sources, such as Cygnus A, show evidence for a geometrically thick “torus” as originally suggested, recent work on the radiation-driven warping instability discovered by Pringle suggests that obscuration by thin, warped disks may play a crucial role in AGN.

BACKGROUND Suicide risk among U.S. military personnel has been increasing over the past decade. Fluid vulnerability theory (FVT; Rudd, 2006) posits that acute suicidal episodes increase in severity when trait-based (e.g., shame) and state-based (e.g., hopelessness) risk factors interact, especially among individuals who have been previously suicidal. In contrast, trait-based protective factors ...

A careful analysis of the gravitational geon solution found by Brill and Hartle is made. The gravitational wave expansion they used is shown to be consistent and to result in a gauge invariant wave equation. It also results in a gauge invariant effective stress-energy tensor for the gravitational waves provided that a generalized definition of a gauge transformation is used. To leading order th...